1. Field of the Invention
The present invention generally relates to an apparatus and methods for drilling, completion and rework of wells. More particularly, the invention relates to an apparatus and methods for activating and releasing downhole tools. More particularly still, the invention provides a hydraulically activated downhole tool.
2. Description of the Related Art
In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling a predetermined depth, the drill string and bit are removed, and the wellbore is lined with a string of steel pipe called casing. The casing provides support to the wellbore and facilitates the isolation of certain areas of the wellbore adjacent hydrocarbon bearing formations. The casing typically extends down the wellbore from the surface of the well to a designated depth. An annular area is thus defined between the outside of the casing and the earth formation. This annular area is filled with cement to permanently set the casing in the wellbore and to facilitate the isolation of production zones and fluids at different depths within the wellbore.
It is common to employ more than one string of casing in a wellbore. In this respect, a first string of casing is set in the wellbore when the well is drilled to a first designated depth. The well is then drilled to a second designated depth, and a second string of casing, or liner, is run into the well to a depth, whereby the upper portion of the second liner is overlapping the lower portion of the first string of casing. This process is typically repeated with additional casing strings until the well has been drilled to total depth. To properly place the additional casing strings within the wellbore, the end of the existing casing must be determined. A downhole tool, such as a tubing end locator, is typically employed to accurately locate the end of the existing casing.
Typically, a conventional tubing end locator is run downhole on a tubing string. The end of the tubing is indicated when the tubing end locator runs out the end of the tubing and is then brought back uphole, thus shearing the finger and indicating the depth of the tubing. Therefore, conventional tubing end locators employing calipers, fingers or other protrusions are capable of only reading the end of the tubing once, and thus yield a low level of accuracy as to the depth of the tubing. Consequently, when a conventional tubing end locator is run downhole and brought back uphole at the tubing end, the caliper or finger is sheared completely off thus indicating the end of the tubing and destroying the caliper or finger and requiring the tubing end locator to be brought back uphole to be re-worked or retooled.
A conventional tubing end locator may also be used to locate a preformed inner diameter profile, a collar or a nipple in an existing downhole casing. Conventional tubing end locators implement calipers or fingers which extend vertically upward and outwardly from the tubing end locator such that each caliper or finger is spring loaded and exerts an external pressure against the internal diameter and circumference of the tubing. Each caliper or finger deflects at each inner diameter profile juncture, thus indicating the location of the preformed profile, collar or nipple is located.
Another form of a conventional tubing locator employs the use of bow springs to locate a preformed inner diameter profile, a collar or a nipple in an existing downhole casing. The locator tool includes high compressive springs and a set of bow springs extending radially from a mandrel on the tool. The bow springs extend vertically, longitudinally and radially outward from the mandrel thus contacting the internal circumference and surface of the casing or tubing, and establishing a constant internal resistance detected uphole at the surface. When the bow springs contact a preformed inner diameter profile, a collar, a nipple or tubing end, the bow springs will move either upwardly towards the surface at each collar indication, or downwardly towards the end of the tubing at each tubing end indication.
Several problems may occur using a conventional tubing locator during a locator operation. One problem occurs when an excessive overpull is applied at the surface of the well during the location of the preformed inner diameter profile, collar, nipple or tubing end. In this case, the conventional tubing locator does not provide a failsafe mechanism that allows the locator tool to release and reset after applying the excessive overpull. Another problem occurs during the indication phase of the locator operation. After the conventional tubing locator has located the profile or tubing end, an overpull indication must be detectable at the surface of the well. However, the conventional tubing locator tool is unable to withstand an overpull that is easily detectable at the surface, therefore unable to accurately to determine the location of the profile.
Other downhole tools are used throughout the well completion process. One such downhole tool is a conventional under-reamer. Generally, the conventional under-reamer is used to enlarge the diameter of wellbore by cutting away a portion of the inner diameter of the existing wellbore. A conventional under-reamer is typically run down hole on a tubing string to a predetermined location with the under-reamer blades in a closed position. Subsequently, fluid is pumped into the conventional under-reamer and the blades extend outward into contact with the surrounding wellbore. Thereafter, the blades are rotated through hydraulic means and the front blades enlarge the diameter of the existing wellbore as the conventional under-reamer is urged further into the wellbore.
The conventional under reamer may also be used in a back-reaming operation. In the same manner as the under-reaming operation, the fluid is pumped into the under-reamer and the blades extend outward into contact with the surrounding wellbore. Thereafter, the blades are rotated through hydraulic means and the back blades enlarge the diameter of the existing wellbore as the under-reamer is urged toward the surface of the wellbore.
Several problems may occur using a conventional under-reamer during an under-reaming or back-reaming operation. One problem occurs when an unmovable obstruction is encountered during the under-reaming or back-reaming operation. In this situation, the front or the back blades on the conventional under-reamer may be damaged as the under-reamer is urged furthered toward the unmovable obstruction. Another problem is particularly associated with the back-reaming operation. During the back-reaming operation, the blades must remain open and the under-reamer must be able to withstand a strong pulling force to effectively remove a portion of the existing wellbore diameter. However, the conventional under-reamer typically is unable to remain open during a back-reaming operation to effectively enlarge the wellbore diameter.
A need therefore exists for apparatus with a hydraulic valving system that provides a failsafe mechanism that allows the apparatus to withstand a sufficient overpull while permitting the apparatus to release and reset after applying an excessive overpull. There is yet a further need for an apparatus with a hydraulic valving system that will provide a failsafe mechanism that allows the apparatus to close when an unmovable obstruction is encountered. There is a final need for an apparatus with a hydraulic valving system that ensures the apparatus will remain open during a back-reaming operation.
The present invention provides a method and an apparatus for use in a wellbore tool. The apparatus includes a body having a center bore and at least one side port permitting fluid communication between the bore and an annular area between the tool and the wellbore. The apparatus further includes a sliding member, wherein the sliding member moves between a first position and a second position and a valve assembly that causes the sliding member to shift to its second position at a predetermined flow rate of fluid through the body. The apparatus also includes a mechanical portion movable with the sliding member between the first and second positions.
In another embodiment, the invention provides for an apparatus for a downhole tool that includes a mandrel, a plurality of ramped sections radially disposed around the mandrel and a plurality of longitudinal grooves radially disposed between the plurality of ramped sections. The invention further includes a sliding member disposed on the mandrel, the sliding member movable between a first and second position the sliding member including a plurality of fingers and a plurality of heads, wherein the plurality of fingers are slideably recessed within the plurality of longitudinal grooves.
In another embodiment, the invention provides a collet assembly for use in a wellbore, the collet assembly includes a body and at least two extendable members movable independent of the body, the members are extendable outwards. The collet assembly further includes a sliding member attached to each member, the sliding member remotely movable between a first and second position. The collet assembly also includes a ramp formed on the body whereby, the members are urged along the surface to extend outwards and as the members are extended outwards, the members are rotated.